Method and device for monitoring data processing and transmission in a security chain of a security system

A method for monitoring data processing and data transmission in a safety chain of a safety system, wherein the safety system provides an overall safety function and is composed, in a modular manner, of at least two subsystem modules, and wherein at least the two subsystem modules are connected to a data transfer channel and each provide a partial safety function and are configured for functionally safe data processing and/or data transmission, comprising the steps of:

• processing data by a first one of the subsystem modules to obtain functionally safe data;
• determining, by said first subsystem module, a first actual characteristic value for a safety-relevant characterizing attribute of the data processing and/or data transmission, in particular for a total response time;
• transmitting the functionally safe data and the first actual characteristic value from said first subsystem module to a second one of the subsystem modules, and receiving the functionally safe data and the first actual characteristic value by said second subsystem module;
• determining, by said second subsystem module, a second actual characteristic value for the safety-relevant characterizing attribute;
• processing the first actual characteristic value and the second actual characteristic value so as to obtain a third actual characteristic value for the safety-relevant characterizing attribute, by said second subsystem module;
• determining, by said second subsystem module, a nominal characteristic value for the safety-relevant characterizing attribute;
• comparing said third actual characteristic value with the nominal characteristic value of the safety-relevant characterizing attribute, by said second subsystem module, and, depending on the comparison result,
• if the result of the comparison is positive, further processing and/or forwarding the functionally safe data;
• or
• if the result of the comparison is negative, triggering a predefined safety reaction.